Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 301446
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1046 AM EDT SAT JUL 30 2016
A typical mid-summer weekend is on tap for the region as a broad and
weak pressure pattern lingers atop the Southeast. Little change in
the weather pattern is expected through the start of next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM Saturday: Made several adjustments mainly to sky and
pop grids to account for continued midlevel cloudiness moving across
the Piedmont. Still seeing some returns across the Upstate with
these clouds but mostly virga at this time. An area of convection
that has moved across eastern TN is right on our border so have
adjust pops across the mountains to account for this. Additionally,
another area (actually it`s all along the same impulse) in northern
GA is producing some showers downstream into NE GA. The cloud cover
has held temps down a little more than expected but with afternoon
mixing/clearing the overall high temps should catch up. Made tweaks
to hourly trends with some minor changes to afternoon highs but
changes are mainly negligible.
Otherwise, a broad, yet medium amplitude H5 trof continues to dig
across the east/central CONUS, while the persistent anticyclone that
has been responsible for many dry/hot days over the southeast
flattens. At the surface over the southeast, weak high pressure
looks to prevail overall, however with embedded lee troffing over
portions of Northeast GA and the western Carolinas.
Thermal profiles once again exhibit modest low/mid lvl lapse
rates beneath poor rates in the mid/upper levels, while shear is
slightly improved from days past thanks improved flow amidst the
synoptic trof. Given these parameters, as well as an analysis
of Cam composites, the fcst will feature a broad brush of
isolated/scattered thunderstorms this afternoon, likely initiating
along the Blue Ridge before cold pool propagation directs said
convection east into the NC/SC piedmont. Given the poor lapse
rates aloft, not expecting any severe convection, however a few
stronger storms cannot be ruled out. Pops will lower through the
evening into the overnight, however lingering at low end slight
chance levels regionwide through Sunday morning. Temperatures today
will once again be quite warm, generally mid/upper 90s along/south
of I85, with upper 80s to lower 90s across the northern piedmont
and foothills, and upper 70s to mid 80s favored over the higher
elevations. Dewpoints are expected to mix out a bit into the
afternoon, however remaining at levels supportive of heat indices
nearing the century mark across the southern tier of the fcst area.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 155 AM Saturday...an upper trough axis moves into the area
Sunday and remains in place on Monday. A series of weak short waves
will rotate through the trough and over or near the area each day.
At the surface, a weak cold front moves toward the area Sunday with
a lee trough developing over the CWFA. The front drops into the area
for Monday. All this should lead to a relatively good environment
for deep convection both days. Therefore, precip chances will be
higher then climo, but with a fairly typical diurnal and placement
trend. Cannot rule out a few strong/severe storms both days, but
poor lapse rates, low shear, and relatively weak DCAPE suggest
chances are low. Temps will remain above normal with low to mid 90s
common both days. Humidity will be high enough for heat index values
to rise into the low 100 range, mainly south of I-85.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 320 AM Saturday...upper trough axis over the East Coast on
Tuesday slides off shore on Wednesday as ridging builds over the
central CONUS. This keeps a NW flow over the area through Thursday
allowing a series of short waves to move through the flow and over
or near the CWFA. Differences develop in the guidance by Friday,
with the ECMWF showing short wave ridging developing over the area,
while the GFS develops a weak short wave trough. A quasi-stationary
front remains over the area Tuesday and Wednesday keeping a chance
of diurnal convection over the CWFA each day. Tuesday is the drier
of the two days with only isolated convection expected. The front
washes out Thursday but southerly low level flow develops and
continues into Friday. This keeps moisture and instability over the
area, resulting in continued scattered mainly diurnal convection
each day. Temps remain above normal through the period, but do drop
toward normal for Thursday.
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
At KCLT: Only change for the 15z AMD was to remove VCSH until
18z. Winds have already started veering more to the W as the lee
trough sets up again so the WSW winds look good. Otherwise, VFR
through the period. Mid/high clouds giving way to few/sct low vfr cu
this afternoon. Profiles today remain relatively unstable in the
low/mid levels, however exhibit poor lapse rates in the mid/upper
levels which would limit overall depth/intensity of tsra. Therefore,
still thinking convection will initiate about the region by
early/mid afternoon therefore previous prob30 was dropped in favor
of a 4hr tempo from 19-23z. Winds will remain light wnw/wsw this
morning before backing sw by late morning in the 6-8kts range.
Elsewhere: Trends very similar to that of KCLT above, however with
early restrictions due to fog/cigs by way of brief tempos at KHKY
and KAVL. Light shra is trying to establish itself across the
Upstate at this time thus did decide to prevail VCSH through the
next few hours at all SC sites. Otherwise, mid/high clouds will
prevail through late morning before low vfr cu develops at all
sites. Kept all tsra mention in by way of vcts/prob30 with timing
based upon latest cams. Winds will remain generally out of the
wsw around 6-10kts aside for at KAVL where wnw flow will prevail.
Outlook: Broad troffing continues to build across the east/central
CONUS lasting into mid week. Moisture in the low/mid levels
combined with a series of impulses working through the mean flow
aloft will yield continued/increased chances for shra/tsra through
mid/late week. As such, restrictions associated with shra/tsra
are possible, as well as early morning fog/cigs.
14-20Z 20-02Z 02-08Z 08-12Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 88% High 100% High 100% Med 70%
KHKY High 100% High 100% High 100% High 87%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: